The invention relates to a bellows disposed on a guide member of a disc brake.
Bellows are provided to protect the guide members on which, for example, the brake caliper of a sliding-caliper disc brake is mounted displaceably, which bellows are fastened at their ends respectively to the guide member and to the component which is movable relative thereto, for example the brake caliper.
Dirt is thereby prevented from entering the slide region and thus degrading or destroying the sliding properties thereof. The same applies to moisture which might otherwise penetrate and lead to corrosion damage.
The bellows is retained at one end in a form-fitting manner on the guide member, for which purpose it has at the associated end a sealing ring which engages in a circumferential groove of the guide member and is secured in this position.
At the other end, the bellows is retained in the brake caliper and sealed with respect to the guide member by a sealing lip, which bears circumferentially against the guide member. The abutment of the bellows against the guide member at both ends produces a practically airtight closure which, however, gives rise to considerable disadvantages.
As the brake caliper is displaced relative to the guide member, the volume of the region enclosed by the bellows changes. However, the air cannot escape to the outside and inflates the bellows, the sealing lip being pressed against the guide member by the overpressure produced, resulting in an especially firm, airtight abutment of the sealing lip against the guide member.
Especially during changing of a brake pad, when the brake caliper is displaced along the guide member in a very short time, damage to the bellows can occur, above all when a new replacement brake pad is installed.
In this case replacement of the bellows is urgently necessary, since otherwise its protective function is not ensured.
Furthermore, purely functional problems are created by the airtight connection. An inflated bellows acts as an air spring which presses the brake pad against the brake disc of the disc brake, so that the brake pad rests constantly against the brake disc while the vehicle is moving, which can cause hot-running of the brake with the resulting problems, especially with regard to safety.
It is the object of the invention to develop a bellows such that the overall functional and operating safety of the disc brake is improved.
This and other objects are achieved by a bellows disposed on a guide member of a disc brake, in particular of a commercial vehicle, which bellows has arranged at one end a circumferential sealing lip, which bears sealingly against the guide member in a functional position. The sealing lip is connected rigidly to the adjacent corrugation.
This configuration of the bellows ensures that when it is compressed an air pressure equalization takes place, since, on account of the inflation of the whole bellows through overpressure, the rigid connection of the sealing lip to the adjacent corrugation causes the sealing lip to be lifted from the guide member, so that the, so to speak, excess air quantity can escape without difficulty.
In the case, above all, of the rapid compression of the bellows described in relation to the prior art, which occurs typically when exchanging brake pads, a pressure equalization between the interior chamber enclosed by the bellows and the environment now takes place immediately.
As this happens the sealing lip acts like a nonreturn valve, since the sealing lip, on account of the restoring forces, again rests sealingly against the guide member over its full circumference after a pressure equalization has taken place.
According to an advantageous development of the invention, the rigid connection of the sealing lip to the adjacent corrugation can be produced by integrally molded webs which bridge the gap present between the sealing lip and the adjacent corrugation.
In the case of a two-part configuration of the sealing lip and the bellows, separate webs, which are connected form-fittingly both to the bellows and to the sealing lip, may be provided. It is also possible to mold the webs integrally on the sealing lip or the bellows, each being seen as a separate part, and to connect the webs form-fittingly to the respective other part.
The number and dimensioning of the webs may vary and are essentially dependent on the object concerned.
The brake pad wear described in relation to the prior art is now effectively prevented, as is the inflation of the bellows while exchanging brake pads, whereby the danger of damage to the bellows is practically eliminated.
Since, moreover, the bellows is only compressed but is not extended in operation, and therefore only the production of increased internal pressure must be prevented by the invention, measures which would necessitate a pressure equalization upon extension of the bellows do not need to be provided, so that the invention can be implemented with extremely simple means.
Self-evidently, this implies that cost and complexity can be kept very low and that manufacture and assembly can therefore be extremely cost-effective, so that the invention can be implemented basically in a cost-neutral manner.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.